Ugh, those things are so nasty. I had the same problem with these bugs on my tomatillo plants too, though unfortunately, I didn't take any steps to eradicate them--except shaking the beetles off and then spraying the gross things with diluted soap water, which wasn't very successful. These gross little larvae have eaten their way through all of my tomatillos this year. I have one sickly tomatillo plant left (larvae and poop-ridden), hope there are some suggestions here-I would like to save it and hoping I have some late summer, early fall production.

A google search was helpful. The organic methods I will try are sage/citrus oils and pyola (pyrethrins+canola.)

I picked up a bag of orange peels from Jamba Juice. I am going to try some clever method to get the oils out. Not sure how exactly. ~~~~~~~~~~~~~~~~
Chemical treatments
A few commercial botanical preparations are available for use on CPB. Rotenone is derived from the roots of a South American plant. Since it is somewhat slow at killing pests, it is often combined with pyrethrum for a faster "knockdown." Plant protection is relatively brief, usually lasting two days or less. Rotenone must be used with caution as it is quite toxic to fish and swine. Rotenone is a restricted material, one that should be used only when other, less severe options fail to exert adequate control. Be certain to read the label directions for specific instructions and cautions.

Various products with the active ingredient azadirachtin (from neem tree seeds) have some efficacy against CPB in the early crop stages. These include Neemix, BioNeemÂ, and Margosan-OÂ. However, spray concentrations of 1% and greater may cause phytotoxicity on potato plants. (11) Furthermore, though they were once considered benign to beneficial insects, neem products have demonstrated some negative impacts. Washington State research has found neem to be toxic to ladybeetles, especially in their early larval stages. (12) Meanwhile, research in Maine found neem less effective than Bacillus thuringiensis (see Biopesticides below). (13)

Pyola is a natural insecticide product that combines canola oil with pyrethrins. It is recommended for use on cucumber beetles, flea beetles, Mexican bean beetles, squash bugs, aphids, mites, and CPB. (14) However, since much of the canola oil on the market is derived from genetically engineered plants, this product may or may not be acceptable for organic production. Growers should contact their certifying agent before purchase and use.
A number of herbs and herbal extracts are also reputed to repel or inhibit CPB, though research has been far from thorough. Among the plants believed to have some effect are: catnip, tansy, sage (15), hemp (16), oak extract (17), wild potato (Solanum chacoense) (18), and citrus oils. (19)

Biopesticides
Several biopesticide products based on the bacterium Bacillus thuringiensis (Bt) have become available in recent years. M-OneÂ, made from B. thuringiensis ssp. san diego, is genetically engineered and therefore is not allowed in certified organic production. NovodorÂ, produced by Valent USA Corp. (20), contains B. thuringiensis ssp. tenebrionis, a form of Bt that is not genetically engineered and can be used by organic producers in most states. One source of Novodor is Peaceful Valley Farm Supply. (21)

Bt is effective only if ingested by the pest, and then only in the larval stage. Furthermore, Bt sprays are generally effective only against newly hatched CPB larvae. Applications should be made within one to two days whenever one or both of two criteria are met:
 densities of egg masses reach or exceed 4 per 50 vines and at least 25% of the oldest masses have hatched or are hatching;
 densities of small larvae reach the treatment threshold of 76 per 50 plants or stems. (22)
Bt is most effective if applied when daytime temperatures reach or exceed 75°F, because larval feeding is then increased. (22)

Another biopesticide, MycotrolÂ, is based on the fungal agent Beauveria bassiana. Like Bt, B. bassiana is a naturally occurring organism. Unlike Bt, B. bassiana is effective against all larval and adult stages of CPB. Furthermore, once B. bassiana is applied, it can continue to propagate and provide a significant level of CPB control throughout the remainder of the season. The most significant limitation of B. bassiana appears to be its sensitivity to high temperatures. Mycotrol works best between 70 and 80°F. Growth of the organism is much slower at warmer temperatures. (23) As a result, this may be a poor option for growers in southern states during much of the growing season.

Emerald BioAgriculture Corp. (24), the manufacturer of MycotrolÂ, recommends spraying when hatching occurs in 20-25% of the egg massesÂtiming similar to that for Bt. A possible strategy involves combining Bt with B. bassiana for optimum efficacy. While Bt is effective at killing early-instar larvae, it will also slow the growth of larger larvae and make them more susceptible to the fungus. (23)

Parasitic nematodes are another control option. Commercial formulations of Heterorhabditis species are available and have been shown to be more pathogenic (25), to the CPB than Steinernema species of nematodes, which are also commercially available.